Coating system and method for applying a thermosetting viscous polymer to the inner surface of a pipe

Abstract

A coating system applying a thermosetting viscous polymer to the inner surface of a pipe has a first cart (14) configured to advance inside a pipe ( 2 ); a first heated tank (15), which is carried by the first cart (14) and is configured to contain the base component and to heat the base component to a first temperature; a second tank (16), which is carried by the first cart (14) and is configured to contain the hardener component; a mixer (17) configured to mix the base component and the hardener component so as to form the polymer; a first and a second pump (18, 19) to feed the base component and the hardener component respectively from the first and the second tank (15, 16) to the mixer (17); and an applicator (20) configured to apply the polymer to the pipe (2).

Description

[0001] "COATING SYSTEM AND METHOD FOR APPLYING A THERMOSETTING VISCOUS POLYMER TO THE INNER SURFACE OF A PIPE"

[0002] Cross-Reference to Related Applications

[0003] This Patent Appl ication claims priority from Italian Patent Application No . 102022000026790 filed on December 23 , 2022 , the entire disclosure of which is incorporated herein by reference .

[0004] Field of the Art

[0005] The present invention concerns a coating system and method for applying a thermosetting viscous polymer to the inner surface of a pipe .

[0006] In particular, the present invention concerns a coating system for internally coating a j oint of a metal pipe on site during the laying operations of said pipe on a bed of a body of water, without thereby limiting the wide range of possible applications of the present invention .

[0007] Background of the Invention

[0008] Generally, the laying of pipes on a bed of a body of water is carried out by means of a naval means , which is configured to transport , connect and lay a plurality of pipe sections .

[0009] Before being laid on the bed of the body of water, the ends of the pipe sections are welded together on site , forming a pipe .

[0010] In more detail , one end of a pipe section is welded to one end of the pipe and subsequently the naval means is advanced to allow the launching of said pipe section into the body of water .

[0011] The inner and outer surfaces of each pipe section are coated with at least one coating to prevent corrosion, thermal dispersions and to reduce the pressure drops of the transported fluid .

[0012] Such a coating is generally applied to each pipe section during the manufacture step, within a pipe section manufacture plant .

[0013] However, the end portion of each pipe section is without coating as the high temperatures due to welding could damage the coating .

[0014] Consequently, the inner and outer surfaces of the end welded to the pipe of each pipe section must be coated on site after welding .

[0015] Generally, the coating is made by applying a polymer comprising a base component and a hardener component to the inner surface of the pipe section at a temperature ranging in a predetermined interval . By way of example , the polymer may consist of an epoxy resin .

[0016] Document WO 2021 / 009709 describes a system for internally coating a pipe on site by applying a polymer composed of a bi-component and thermosetting epoxy resin .

[0017] However, due to the severe operating conditions to which the pipe may be subj ected, the inner coating of the pipe may be subj ect to undesired phenomena leading to a degradation of the protective barrier function of the coating .

[0018] In particular, the partial pressure of volatile molecules transported in gases such as hydrogen and / or carbon dioxide and / or sulphur dioxide contained in the product transported by the pipe in combination with the variable pressures to which the pipe may be subj ected during its operating li fe , may lead these molecules to penetrate and / or spread in the coating, and subsequently it may cause undesired phenomena, normally called "blistering" , which lead to a degradation of the barrier functions of the coating .

[0019] To overcome these drawbacks , it is possible to use bicomponent and thermosetting polymers with an innovative composition, characteri zed by a higher viscosity and by a higher concentration of the base component . However, having a high viscosity, such polymers make the workability and the application of the polymer to the inner surface of the pipe to be coated critical .

[0020] Object of the Invention

[0021] Aim of the present invention is to reali ze a coating system for applying a thermosetting viscous polymer to the inner surface of a pipe that mitigates the drawbacks of the prior art .

[0022] In accordance with the present invention, it is reali zed a coating system for applying a thermosetting viscous polymer comprising a base component and a hardener component to the inner surface of a pipe , the system comprising a polymer application unit , which comprises :

[0023] - a first cart configured to advance inside a pipe in a direction parallel to the longitudinal axis of the pipe ;

[0024] - a first heated tank, which is carried by the first cart and is configured to contain the base component and to heat the base component to a first temperature ;

[0025] - a second tank, which is carried by the first cart and is configured to contain the hardener component ;

[0026] - a mixer configured to mix the base component and the hardener component so as to form the polymer ;

[0027] - a first and a second pump to feed the base component and the hardener component respectively from the first and the second tank to the mixer ;

[0028] - an applicator configured to apply the polymer to the pipe ; and

[0029] - a supply conduit configured to feed the polymer from the mixer to the applicator .

[0030] Thanks to the present invention, it is possible to internally coat the pipe with a bi-component polymer with high viscosity and with chemical-physical characteristics that guarantee optimal and lasting protection over time to the pipe to which it is applied .

[0031] In particular, the viscosity of the base component decreases with increasing temperature of the base component . Thanks to the first tank, it is possible to transport the base component on board the application unit , maintaining the base component above a determined temperature and, consequently, reducing the viscosity of the base component . In this way, it is possible to feed the base component from the first tank to the mixer and apply the polymer through the applicator without the risk of fluid dynamic irregularities arising in the base component and in the polymer, such as for example blockages due to the high viscosity of the base component .

[0032] In particular, the second tank is heated and is configured to heat the hardener component to a second temperature .

[0033] In this way, it is possible to control also the viscosity of the hardener component .

[0034] In particular, the first tank is pressuri zed so as to keep the base component under pressure .

[0035] In this way, it is possible to favour the complete emptying of the first tank and, consequently, increase the number of applications of the coating without refil ling the first tank with the base component . In other words , it is possible to fully exploit the capacity of the first tank .

[0036] In particular, the first tank comprises a rotating mixing device configured to mix the base component inside the first tank .

[0037] Thanks to the rotating mixing device , it is possible to make the temperature of the base component inside the first tank uni form and to contribute to the complete emptying of the first tank .

[0038] In particular, the applicator comprises a rotating body, preferably of a discoidal shape , configured to centri fugally dispense the polymer onto the inner surface of the pipe .

[0039] In this way, it is possible to evenly di f fuse the polymer on the inner annular surface of the pipe . In particular, the supply conduit is provided with a free end configured to be disposed in proximity to the applicator .

[0040] In more detail , the application unit comprises a drip tray for the polymer and a rotating shaft , which is connected to the rotating body and is configured to rotate about a rotational axis so as to control the rotation of the rotating body, the rotating body being slidable along the rotational axis so that the free end of the supply conduit selectively feeds polymer to the rotating body or to the drip tray .

[0041] In this way, when the application of the coating is interrupted, it is possible to purge the polymer in the drip tray .

[0042] A further aim of the present invention is to realise a coating method for applying a thermosetting viscous polymer on the inner surface of a pipe which mitigates the drawbacks of the known art .

[0043] In accordance with the present invention it is reali zed a coating method for applying a thermosetting viscous polymer comprising a base component and a hardener component to the inner surface of a pipe , the method comprising the steps of :

[0044] - advancing a polymer application unit inside a pipe in a direction parallel to the longitudinal axis of the pipe ;

[0045] - heating the base component to a first temperature in a first tank of the application unit ;

[0046] - containing the hardener component in a second tank of the application unit ; feeding the base component and the hardener component respectively from the first and the second tank to a mixer ;

[0047] - mixing the base component and the hardener component to form the polymer ; and - applying the polymer to the pipe by means of an applicator .

[0048] Thanks to the present method, it is possible to internally coat the pipe with a high viscosity bi-component polymer transported on board the application unit . In particular, it is possible to heat the base component above a determined temperature in the first tank, thereby reducing the viscosity of the base component and facilitating the management of the base component during operations of application of the polymer .

[0049] Brief Description of the Drawings

[0050] Further features and advantages of the present invention will become clear from the following description of a non-limiting embodiment example thereof , with reference to the accompanying Figures , wherein :

[0051] - Figure 1 is a schematic representation of a coating system for applying a thermosetting viscous polymer to the inner surface of a pipe reali zed in accordance with the present invention, in a particular operating configuration;

[0052] - Figure 2 is a perspective view, with parts removed for clarity ' s sake , of a detail of the coating system of Figure 1 ;

[0053] - Figure 3 is a perspective view, with parts removed for clarity ' s sake , of a further detail of the coating system of Figure 1 ;

[0054] - Figure 4 is a schematic representation of a detail of the coating system of Figure 1 ; and

[0055] Figure 5 is a schematic representation of the coating system of Figure 1 in a further operating configuration .

[0056] Detailed Description of the Figures

[0057] With reference to Figure 1 , 1 denotes as a whole a coating system for applying a thermosetting viscous polymer to the inner surface of a metal pipe 2 having a longitudinal axis Al . In particular, the polymer comprises a base component and a hardener component .

[0058] In the case described and shown herein, the coating system 1 is used to internally coat on site a j oint 3 of the pipe 2 during the laying operations of said pipe 2 on a bed of a body of water, without thereby limiting the wide range of possible applications of the present invention .

[0059] The coating system 1 comprises a finishing unit 4 for the inner surface of the pipe 2 , configured to prepare the inner surface of the pipe 2 for the application of a polymer ; a polymer application unit 5 , configured to apply the polymer on the inner surface of the pipe 2 ; and a locomotion unit 6 configured to move inside the pipe 2 the finishing unit 4 and the polymer application unit 5 along a direction D parallel to the longitudinal axis Al .

[0060] The finishing unit 4 , the polymer application unit 5 and the locomotion unit 6 are connected to each other .

[0061] In the case shown in Figure 1 , the finishing unit 4 is connected at a first end to the polymer application unit 5 and at a second end to the locomotion unit 6 , but also further connection configurations between the finishing unit 4 , the polymer application unit 5 and the locomotion unit 6 are possible .

[0062] The locomotion unit 6 comprises a cart 7 , which is configured to move within the pipe 2 along the direction D; and a motor group 8 , which is configured to provide the locomotion unit 6 with the necessary propulsion to move the entire coating system 1 within the pipe 2 along the direction D .

[0063] Although in the case of Figure 1 a single locomotion unit 6 is shown, the coating system 1 may comprise a plurality of locomotion units 6 connected to each other .

[0064] The finishing unit 4 comprises at least one tank 9 configured to contain an abrasive material ; a rotating wheel 10 configured to centri fugally emit the abrasive material on the inner surface of the pipe 2 ; an abrasive material recovery device 11 ; and a containment chamber 12 , delimited by two walls 13 and configured to contain the rotating wheel 10 and to delimit the portion of the pipe 2 on which the emission of abrasive material takes place .

[0065] In accordance with an embodiment , not shown in the accompanying Figures , the recovery device 11 comprises an abrasive material suction noz zle , which is slidable along a guide in a direction substantially perpendicular to the longitudinal axis Al and is actuated by an actuator, preferably a pneumatic cylinder, and by a motor, preferably a linear stepper motor, so as to allow the sliding of the suction noz zle along said guide . In more detail , said actuator is configured to move the suction noz zle from a parking position to a working position and said motor is configured to position the suction noz zle at a precise distance from the surface of the pipe 2 .

[0066] The polymer application unit 5 comprises a cart 14 configured to advance inside the pipe 2 in the direction D parallel to the longitudinal axis Al of the pipe 2 ; a heated tank 15 , which is carried by the cart 14 and is configured to contain the base component and to heat the base component to a first temperature ; a tank 16 , which is carried by the cart 14 and is configured to contain the hardener component ; a mixer 17 , preferably static, configured to mix the base component and the hardener component so as to form the polymer ; a pump 18 and a pump 19 to feed respectively the base component and the hardener component from the tank 15 and the tank 16 to the mixer 17 ; an applicator 20 configured to apply the polymer to the pipe 2 ; and a supply conduit 21 configured to feed the polymer from the mixer 17 to the applicator 20 .

[0067] The base component is thermosetting and with high viscosity . In particular, the viscosity of the base component decreases with increasing temperature of the base component . The hardener component is a catalyst configured to cause the polymeri zation of the polymer when the hardener component is mixed with the base component .

[0068] In accordance with an embodiment , non-limiting of the present invention, the polymer is a thermosetting epoxy resin . The "MaxEpoxy" product from the company TechnoFink Inc . 21625 Rhodes Rd . Spring, TX 77388 is particularly suitable for this purpose .

[0069] In particular, the tank 15 is configured to heat the base component to a temperature above 30 ° C, preferably to a temperature ranging between 40 ° C and 50 ° C .

[0070] In accordance with an embodiment , non-limiting of the present invention, the tank 16 is heated and configured to heat the hardener component to a second temperature .

[0071] In the case described and shown herein, the tanks 15 and 16 are fixed to the cart 14 and feed the respective pumps 18 and 19 , which are fixed to the cart 14 .

[0072] In accordance with an embodiment , the supply conduit 21 is provided with a free end configured to be disposed in proximity to the applicator 20 .

[0073] The polymer application unit 5 further compri ses a feed valve 22 configured to selectively interrupt the feeding of the base component and of the hardener component to the mixer 17 so as to prevent mixing of the base component with the hardener component ; two electric motors 23 and 24 , which are fixed to the cart 14 and control the respective pumps 18 and 19 ; a heated tube 25, which is configured to hydraulically connect the tank 15 to the mixer 17 and to maintain the base component at a first temperature ; and a heated tube 26 , which is configured to hydraulically connect the tank 16 to the mixer 17 and to maintain the hardener component at a second temperature .

[0074] In particular, the feed valve 22 may be of the pneumatic type or of the solenoid type .

[0075] Furthermore , the polymer application unit 5 comprises a recirculation valve 37 hydraulically connected to the tube 25 ; a recirculation valve 38 hydraulically connected to the second tube 26 ; and a tube 27 and a tube 28 , which hydraulically connect the recirculation valves 37 and 38 respectively to the tanks 15 and 16 and allow recirculation of the base component and of the hardener component in the tanks 15 and 16 .

[0076] In particular, the recirculation valve 37 is configured to selectively allow / block the feeding of the base component to the tube 27 and the recirculation valve 38 is configured to selectively allow / block the feeding of the hardener component to the tube 28 .

[0077] In more detail , the tube 27 and the tube 28 are heated to respectively maintain the base component at a first temperature and the hardener component at a second temperature .

[0078] In accordance with an embodiment , non-limiting of the present invention, the mixer 17 , the feed valve 22 and the recirculation valves 37 and 38 are heated .

[0079] In more detail , the application unit 5 comprises at least one heat exchange device , not shown in the accompanying Figures , configured to regulate the temperature of the base component and of the hardener component in the tanks 15 and 16 and / or inside the tubes 25 , 26 , 27 and 28 and / or in the mixer 17 and / or in the feed valve 22 and / or in the recirculation valves 37 and 38 .

[0080] In more detail , the polymer application unit 5 comprises a plurality of temperature sensors to measure the temperature of the base component in the tank 15 , in the pump 18 , in the tube 25 , in the tube 27 , in the mixer 17 , in the feed valve 22 and in the recirculation valve 37 and to measure the temperature of the hardener component in the tank 16 , in the pump 19 , in the tube 26 , in the tube 28 , in the mixer 17 , in the feed valve 22 and in the recirculation valve 38 . Furthermore , the polymer application unit 5 comprises a cart 39 , which is slidingly coupled to the cart 14 and is provided with a moving mechanism 40 configured to control a sliding of the cart 14 with respect to the cart 39 in a direction substantially parallel to the longitudinal axis Al of the pipe 3 .

[0081] In particular, the cart 39 is directly connected to the finishing unit 4 . The moving mechanism 40 is configured to move the cart 14 along the longitudinal axis Al with respect to the finishing unit 4 and to the locomotion unit 5 during the application step of the polymer to the inner surface of the pipe 3 .

[0082] With reference to Figure 2 , a detail of the tank 15 is shown . In particular, the tank 15 is pressuri zed so as to maintain the base component under pressure . In more detail , the tank 15 is configured to maintain the base component at an overpressure ranging between 0 . 2 bar and 0 . 7 bar with respect to the air pressure at sea level .

[0083] In the case described and shown herein, the tank 15 is delimited by an at least partially rounded casing 29 to facilitate the flow of base component exiting from the tank 15 , avoiding stagnation phenomena .

[0084] Further, the tank 15 comprises a rotating mixing device 31 configured to mix the base component inside the tank 15 . In particular, the tank 15 is provided with a motor 32 , which is configured to control the rotation of the rotating mixing device 31 and is supported by the casing 29 .

[0085] With reference to Figure 3 , the applicator 20 comprises a rotating body 33 of a discoidal shape , configured to centri fugally dispense the polymer onto the inner surface of the pipe 2 .

[0086] Furthermore , the polymer application unit 5 comprises a drip tray 34 for the polymer, which is arranged at the free end of the supply conduit 21 ; a rotating shaft 35 , which extends along a rotational axis A2 and is connected to the rotating body 33 ; and a motor 36 , preferably electrically driven, mechanically coupled to the rotating shaft 35 and configured to control the rotation of the applicator 20 .

[0087] In particular, the rotating body 33 is slidable along the rotational axis A2 so that the free end of the supply conduit 21 selectively feeds the polymer to the rotating body 33 or to the drip tray 34 .

[0088] In more detail , the polymer application unit 5 comprises a sliding mechanism, not shown in the accompanying Figures , configured to actuate the sliding of the rotating shaft 35 and of the rotating body 33 along the rotational axis A2 .

[0089] In accordance with an embodiment , not shown in the preceding claims , the sliding mechanism comprises a motor and worm screw kinematics .

[0090] With reference to Figure 4 , the polymer application unit 5 comprises a plurality of electrical resistors 41 configured to heat the tank 15 , a plurality of temperature sensors 42 configured to measure the temperature of the base component inside the tank 15 , and a level sensor 43 configured to measure the level of the base component inside the tank 15 .

[0091] It is understood that the number of electrical resistors 41 and the number of temperature sensors 42 may vary according to particular operational needs , without thereby departing from the scope of the present invention .

[0092] Furthermore , the polymer application unit 5 comprises a conduit 44 configured to feed a pressuri zed gas , preferably pressurized air, to the tank 15 . The conduit 44 comprises a pressure regulating valve 45 configured to regulate the pressure of the gas fed to the tank 15 , and preferably a non-return valve 46 .

[0093] Furthermore , the polymer application unit 5 comprises a calibration valve 47 , which is coupled to the tank 15 and is configured to calibrate the pressure inside the tank 15 .

[0094] In the case described and shown herein, the polymer application unit 5 further comprises a vent valve 48 , which is coupled to the tank 15 and is configured to discharge the pressuri zed gas outside the tank 15 in the event that the pressure of the gas in the tank 15 exceeds a determined threshold . In accordance with an embodiment , the vent valve 48 is configured to allow the entry of the base component into the tank 15 .

[0095] In use and with reference to Figure 1 , the coating system 1 is introduced into the pipe 2 and is moved through the locomotion unit 6 to slide along the direction D and dispose the finishing unit 4 in proximity to the j oint 3 .

[0096] In more detail , the finishing unit 4 is moved inside the pipe 2 so that the j oint 3 is enclosed between the walls 13 of the containment chamber 12 .

[0097] Subsequently, the abrasive material is fed from the tank 9 to the rotating wheel 10 , which by rotating centri fugally emits the abrasive material on the inner surface of the pipe 2 at the j oint 3 in order to eliminate the irregularities of the inner surface of the pipe 2 caused by the welding process so as to favour the subsequent application of the polymer .

[0098] The abrasive material is recovered by the recovery device 11 to be optionally reused later in a further finishing process .

[0099] At the end of the finishing process , the coating system 1 is again moved by the locomotion unit 6 along the direction D, to arrange the applicator 20 in proximity to the j oint 3 and start the process of application of the polymer .

[0100] In this step, the tank 15 heats the base component in its inside to a first temperature , in particular to a temperature above 30 ° C, preferably to a temperature ranging between 40 ° C and 50 ° C .

[0101] In particular, to favour the heating of the base component , the motor 32 controls the rotation of the rotating mixing device 31 so as to make the temperature of the base component inside the tank 15 uni form .

[0102] In parallel , the pump 18 feeds the base component to the tube 25 and the recirculation valve 37 blocks the feeding of the base component to the mixer 17 , directing the flow of the base component into the tube 27 so as to cause the recirculation of the base component and allow the base component to reach the determined temperature before being fed to the mixer 17 .

[0103] Similarly, the pump 19 feeds the hardener component to the tube 26 and the recirculation valve 38 blocks the feeding of the hardener component to the mixer 17 , directing the flow of the hardener component into the tube 28 so as to cause the recirculation of the hardener component and allow the hardener component to reach the determined temperature before being fed to the mixer 17 .

[0104] Once the determined temperature is reached, the recirculation valves 37 and 38 are actuated so as to block the feeding of the base component and of the hardener component to the tubes 27 and 28 and to direct the flow of the base component and the flow of the hardener component to the mixer 17 .

[0105] In this step, the pumps 18 and 19 feed the base component and the hardener component respectively from the tanks 15 and 16 to the mixer 17 through the tubes 25 and 26 .

[0106] The motors 23 and 24 respectively control the pumps 18 and 19 independently, in order to regulate the flow rates of the base component and of the hardener component fed to the mixer 17 .

[0107] In the mixer 17 , the base component and the hardener component are mixed to form the polymer to be applied to the inner surface of the pipe 2 .

[0108] During these steps , the tubes 25 and 26 , the feed valve 22 , the recirculation valves 37 and 38 and the mixer 17 are heated so as to maintain the base component and the hardener component at the respective determined temperatures .

[0109] The polymer obtained by mixing the base component and the hardener component is fed from the mixer 17 to the conduit 21 , which in turn feeds the applicator 20 through the free end of the conduit 21 .

[0110] The rotating body 33 of the appl icator 20 is rotated by the motor 36 through the rotating shaft 35 and centri fugally emits the polymer on the inner surface of the pipe 2 at the j oint 3 .

[0111] During this step, the moving mechanism 40 controls the position of the cart 14 by actuating the sliding of the cart 14 with respect to the cart 39 along the longitudinal axis Al . In this way, it is possible to position with precision the applicator 20 at the portion of the inner surface to be coated without the need to move the cart 39 , the finishing unit 4 and the locomotion unit 6 .

[0112] With reference to Figure 5 , during a prolonged interruption of the coating operations , the sliding mechanism actuates the sliding of the rotating body 33 along the rotational axis A2 away from the tanks 15 and 16 , so that the free end of the supply conduit 21 feeds the polymer to the drip tray 34 . In practice , when the rotating body 33 slides along the rotational axis A2 moving away from the tanks 15 and 16 , the polymer falls by gravity into the drip tray 34 , which is arranged under the free end of the supply conduit 21 .

[0113] It is understood that , although in the present description the coating system 1 is used for the inner coating of j oints 3 of a pipe 2 during the laying operations of the pipe 2 on a bed of a body of water, the coating system 1 can be used for the inner coating of a generic cylindrical body in other application fields .

[0114] It is evident that variations can be made to the present invention without however leaving the scope of protection of the appended claims .

Claims

CLAIMS1. A coating system for applying a thermosetting viscous polymer comprising a base component and a hardener component to the inner surface of a pipe, the system (1) comprising a polymer application unit (5) , which comprises:- a first cart (14) configured to advance inside a pipe (2) in a direction (D) parallel to the longitudinal axis (Al) of the pipe (2) ;- a first heated tank (15) , which is carried by the first cart (14) and is configured to contain the base component and to heat the base component to a first temperature ;- a second tank (16) , which is carried by the first cart (14) and is configured to contain the hardener component ;- a mixer (17) configured to mix the base component and the hardener component so as to form the polymer;- a first and a second pump (18, 19) to feed the base component and the hardener component respectively from the first and the second tank (15, 16) to the mixer (17) ;- an applicator (20) configured to apply the polymer to the pipe (2) ; and- a supply conduit (21) configured to feed the polymer from the mixer (17) to the applicator (20) .

2. The system as claimed in Claim 1, wherein the second tank (16) is heated and is configured to heat the hardener component to a second temperature.

3. The system as claimed in Claim 1 or 2, wherein the first tank (15) is pressurized so as to maintain the base component under pressure.

4. The system as claimed in any one of the foregoing Claims, wherein the first tank (15) comprises a rotating mixing device (31) configured to mix the base component inside the first tank (15) .

5. The system as claimed in any one of the foregoingClaims, wherein the polymer application unit (5) comprises a first and a second motor (23, 24) , preferably electrically driven, configured to control respectively the first and second pump (18, 19) in an independent way so as to vary the respective flow rates.

6. The system as claimed in any one of the foregoing Claims, wherein the polymer application unit (5) comprises a feed valve (22) configured to selectively interrupt the feeding of the base component and of the hardener component to the mixer (17) so as to prevent mixing of the base component with the hardener component.

7. The system as claimed in any one of the foregoing Claims, wherein the polymer application unit (5) comprises a first heated tube (25) , which is configured to hydraulically connect the first tank (15) to the mixer (17) and to maintain the base component at a first temperature; and a second heated tube (26) , which is configured to hydraulically connect the second tank (16) to the mixer (17) and to maintain the hardener component at a second temperature .

8. The system as claimed in Claim 7, wherein the polymer application unit (5) comprises a first recirculation valve (37) hydraulically connected to the first tube (25) ; a second recirculation valve (38) hydraulically connected to the second tube (26) ; and a third pipe (27) and a fourth pipe (28) , which hydraulically connect the first and second recirculation valve (37, 38) to the first and second tank respectively (15, 16) and allow recirculation of the base component and of the hardener component in the first and in the second tank (15, 16) ; the first recirculation valve (37) being configured to selectively allow / block the feeding of the base component to the third tube (27) ; the second recirculation valve (38) being configured to selectively allow / block the feeding of the hardener component to the fourth tube (28) .

9. The system as claimed in Claim 8, wherein the third tube (27) is heated to maintain the base component at a first temperature and the fourth tube (28) is heated to maintain the hardener component at a second temperature.

10. The system as claimed in any one of the foregoing Claims, wherein the applicator (20) comprises a rotating body (33) , preferably of a discoidal shape, configured to centrifugally dispense the polymer onto the inner surface of the pipe ( 2 ) .

11. The system as claimed in Claim 10, wherein the polymer application unit (5) comprises a third motor (36) , preferably electrically driven, configured to control the rotation of the applicator (20) .

12. The system as claimed in Claim 10 or 11, wherein the supply conduit (21) is provided with a free end configured to be disposed in proximity to the applicator (20) .

13. The system as claimed in Claim 12, wherein the polymer application unit (5) comprises a drip tray (34) for the polymer and a rotating shaft (35) , which is connected to the rotating body (33) and is configured to rotate about a rotational axis (A2 ) so as to control the rotation of the rotating body (33) , the rotating body (33) being slidable along the rotational axis (A2) so that the free end of the supply conduit (21) selectively feeds polymer to the rotating body (33) or to the drip tray (34) .

14. The system as claimed in any one of the foregoing Claims, wherein the polymer application unit (5) comprises a second cart (39) , which is slidingly coupled to the first cart (14) and is provided with a moving mechanism (40) configured to control a sliding of the first cart (14) with respect to the second cart (39) in a direction substantially parallel to the longitudinal axis (Al) of the pipe ( 2 ) .

15. A coating method for applying a thermosettingviscous polymer comprising a base component and a hardener component to the inner surface of a pipe, the method comprising the steps of:- advancing a polymer application unit (5) inside a pipe (2) in a direction (D) parallel to the longitudinal axis (Al) of the pipe (2) ;- heating the base component to a first temperature in a first tank (15) of the polymer application unit (5) ;- containing the hardener component in a second tank (16) of the polymer application unit (5) ; feeding the base component and the hardener component respectively from the first and the second tank (15, 16) to a mixer (17) ;- mixing the base component and the hardener component to form the polymer; and- applying the polymer to the pipe (2) by means of an applicator (20) .

16. The method as claimed in Claim 15, and comprising the step of heating the hardener component to a second temperature in the second tank (16) .

17. The method as claimed in Claim 15 or 16, and comprising the step of pressurizing the first tank (15) so as to maintain the base component under pressure.

18. The method as claimed in any one of Claims 15 to17, and comprising the step of mixing the base component inside the first tank (15) by means of a rotating mixing device ( 31 ) .

19. The method as claimed in any one of Claims 15 to18, wherein the polymer application unit (5) comprises a first cart (14) , which carries the first and the second tank (15, 16) , and a second cart (39) slidingly coupled to the first cart (14) , the method comprising the step of controlling a sliding of the first cart (14) with respect to the second cart (39) in a direction substantially parallel to the longitudinal axis (Al) of the pipe (2) .

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